The present invention relates to a sensor system for controlling movement of a door or other moving structure and, more particularly, a non-contact sensor system having a transmitter and a receiver with a control circuit for controlling movement of an overhead door or other moving structure.
Devices used for controlling the movement, particularly the downward movement of a door, such as an overhead door, are well known in the art. The following patents, the subject matter of which are hereby incorporated herein by reference, relate to sensing edges for use with such a door:
U.S. Pat. No. 5,426,293 entitled xe2x80x9cSensing Edge Having A Photoelectric Switch Position Thereinxe2x80x9d
U.S. Pat. No. 5,728,984 entitled xe2x80x9cSensing Safety Edge Systemsxe2x80x9d
U.S. Pat. No. 5,832,665 entitled xe2x80x9cSensing Edgexe2x80x9d and
U.S. Pat. No. 5,962,825 entitled xe2x80x9cUniversal Sensing Edgexe2x80x9d.
In addition, the use of an electric eye positioned near the floor on either side of such a door for the purpose of controlling downward movement of such a door is generally well known in the art.
While the prior art methods for controlling the downward movement of a door all function adequately, there is a need for a more advanced non-contact sensor system for controlling the movement of a door which is not necessarily located proximate to the floor or closing surface. In this manner, movement of the door can be controlled to prevent damage to the door or to other devices, such as the prongs of a forklift, which may be positioned within the path of the door, but not necessarily proximate to the floor. Prior art sensing edges required that the object actually contact or touch the edge to create pressure or to occlude an infrared or other signal in a sheath thereby allowing the door to come into contact with the object. The present invention provides such a non-contact sensor system for a door which extends beyond a leading edge of the door and moves with the door, and which functions to sense the presence of items in the path of a downwardly moving door over substantially the entire range of movement of the door and prevent the door from ever contacting the sensed items.
Briefly stated, the present invention comprises a non-contact sensor system that controls movement of a door moving in a first direction by actuation of a device. The sensor system includes a transmitter extending a predetermined distance beyond a leading edge of the door at a first door end for transmitting a signal toward a second door end. The transmitter is attached to the door by a first moveable member which is capable of engaging a surface when the door closes and moving to a retracted position. The sensor system further includes a receiver extending a predetermined distance beyond the leading edge of the door at the second door end in relative alignment with the transmitter for detecting the signal, and for generating an output signal when the signal is blocked. The receiver is attached to the door by a second moveable member which is capable of engaging the surface when the door closes and moving to the retracted position. The output signal is suppressed when the second moveable member is in the retracted position.